Sturnus

Sturnus is a genus of starlings. As discussed below, the taxonomy of this group is complex, and other authorities differ considerably in which species they place in this genus, and in the species boundaries within Sturnus. The genus name Sturnus is the Latin for 'starling'. This genus has representatives across most of Eurasia and one species, the European starling, has been introduced to South Africa, North America, Australia and New Zealand. The more northerly breeding species are completely or partially migratory, wintering in warmer regions. The Sturnus starlings are terrestrial species; they walk rather than hop, and have modifications to the skull and its muscles for open-bill probing. The latter adaptation has facilitated the spread of this genus from humid tropical southern Asia to cooler regions of Europe and Asia. Starlings nest in holes in trees or buildings. They are omnivorous and mostly feed on the ground; they specialise in taking invertebrates from just below the surface. This is facilitated by the head adaptations mentioned above, which enable the birds to probe with the bill open, closing it to secure prey items. The plumages within this group are variable, but all the species have the starling's familiar triangular wing shape. They are capable of imitating many sounds and they have been recorded mimicking sounds such as that of a squeaky door. The European (the type species) and spotless starlings are particularly closely related, and interbreed to some extent where their ranges overlap in southwestern France and northeastern Spain. The non-migratory spotless starling may be descended from a population of ancestral S. vulgaris that survived in an Iberian refugium during an ice age retreat. Two extant species are recognized: A mating system is vastly different from reproduction. It includes all the benefits and costs that the female weighs when choosing a mate and the competition that males, and sometimes females, go through when trying to win over a mate. The genus Sturnus contains a variety of mechanisms that factor into their complex mating system. There are three major mechanisms that we see in Sturnus species. Sexy son's hypothesis, parental care, and differential allocation are the three mechanisms that factor into this mating system Male Sturnus unicolor individuals face a choice when it comes to the mating season. They can either invest in parental care, through helping feed the young, provide shelter, etc. and be monogynous or they can control many nests at one time, increase the number of matings they engage in and be polygynous. To add to this, much of the time their choice is biological. Sturnus unicolor males are more likely to be polygynous and be less involved in parental care if they have higher levels of testosterone. In addition, females of the Sturnus vulgaris species see a decrease in their fitness if the male is polygynous because there is no assistance in nestling feeding. Offspring success per nest, however, is significantly higher if there is parental care from the male, but males see greater overall fitness when they are polygynous. This is the trade off and the cost/benefit balance that each individual must go through.